1. Field of the Invention
The present invention generally relates to speech and speaker recognition systems and, more particularly, to speech recognition systems including signal processing model substitution.
2. Description of the Prior Art
Many electronic devices require input from a user in order to convey to the device particular information required to determine or perform a desired function or, in a trivially simple case, when a desired function is to be performed as would be indicated by, for example, activation of an on/off switch. When multiple different inputs are possible, a keyboard comprising an array of two or more switches has been the input device of choice in recent years.
However, keyboards of any type have inherent disadvantages. Most evidently, keyboards include a plurality of distributed actuable areas, each generally including moving parts subject to wear and damage and which must be sized to be actuated by a portion of the body unless a stylus or other separate mechanical expedient is employed. Accordingly, in many types of devices, such as input panels for security systems and electronic calculators, the size of the device is often determined by the dimensions of the keypad rather than the electronic contents of the housing. Additionally, numerous keystrokes may be required (e.g. to specify an operation, enter a security code, personal identification number (PIN), etc.) which slows operation and increases the possibility that erroneous actuation may occur. Therefore, use of a keyboard or other manually manipulated input structure requires action which is not optimally natural or expeditious for the user.
In an effort to provide a more naturally usable, convenient and rapid interface and to increase the capabilities thereof, numerous approaches to voice or sound detection and recognition systems have been proposed and implemented with some degree of success. However, variations in acoustic signals, even from a single speaker, which may represent a command present substantial signal processing difficulties and present the possibility of errors or ambiguity of command understanding by the system which may only be partially avoided by substantial increase of processing complexity and increase of response time.
For example, a simple voice actuated system which relies on template matching of the acoustical content of an utterance theoretically requires a particular word or phrase to be input for each command which can be used by each enrolled (e.g. authorized) user. Therefore, even a moderate number of recognizable commands for each of a moderate number of users can require comparison with a very large number of templates while not guaranteeing successful or accurate voice recognition due to variation of the acoustical signal each time a command may be uttered. Conversely, a speaker independent system would only require enrollment of commands to be recognized and a correspondingly reduced number of template comparisons but accuracy of command recognition or understanding by the system would be severely compromised by additional variation of acoustical signals from speaker to speaker.
Accordingly, it can be understood that while improved performance can be expected from a speaker dependent system, such improved performance has heretofore only been achieved at the expense of greater processing complexity and consequent degradation of response time and increased hardware and/or software overhead.